Breast cancer is the most common cancer among American women and the second leading cause of cancer death in women. American Cancer Society, 2007 [1]. However, early detection of breast cancer has been proven to reduce mortality by about 20% to 35%. Elmore et al., 2005 [2]. Histopathological examination is considered to be the “gold standard” for definitive diagnosis of cancer but requires tissue samples that are collected through biopsy. Of the two major approaches for breast biopsy, needle biopsy and open excisional biopsy, needle biopsy is the most commonly practiced because it is less traumatic, produces little or no scar, allows quicker recovery, and is less expensive.
Despite many benefits of needle biopsy, there are significant technical challenges concerning accurate steering and precise placement of a biopsy needle at the target in breast tissue. To successfully remove a suspicious small targeted lump (e.g., less than 5 mm in diameter) various issues must be addressed, such as architectural distortion and target deflection during needle insertion and poor maneuverability of the biopsy needle. These issues are even more important when the collection of a large and intact core becomes necessary for histopathological diagnosis. Currently, large core samples are collected using large needles such as a 14-gauge (2.1 mm in diameter) true cutting needle, a 10-gauge (3.4 mm in diameter) vacuum-assisted needle, and other radiofrequency (RF) cutting instruments (EN-BLOC® and RUBICOR®) that increase insertion force significantly.
Although mammography, sonography, and magnetic resonance imaging (MRI) techniques have significantly improved early detection of breast cancer, accurate placement of a biopsy needle at the target location and reliable collection of target tissue remain challenging tasks.
Needle biopsies are guided by either stereotactic mammography, magnetic resonance imaging (MRI) or ultrasound (US) imaging. Sonography is the most widely used imaging technique because of its real-time capability and cost-effectiveness. For a few years three dimensional (3D) US systems have been available, but they are not as widely used as two dimensional (2D) US systems because of their high cost. 3D reconstruction algorithms have also been developed for real-time 3D rendering of a volume with image data acquired using a 2D US probe. Solberg et al., 2007 [3]. Real-time 3D reconstruction uses pixel data from the current US image slice to update the 3D volume. Hence the entire 3D volume cannot be reconstructed in real-time. To overcome this, researchers have developed techniques to extrapolate 3D volume data using 2D image slices. This technique is not applicable to breast biopsies due to the deformation of the breast during needle insertion.
Despite numerous benefits of needle biopsy, however, there are significant challenges concerning accurate steering and precise placement of a biopsy needle at the target (the word target as used herein refers to a tumor, a lesion or just a suspected region of tissue) in breast tissue. First, as the needle is inserted, large tissue deformation causes the target to move away from the line of insertion of the needle. DiMaio et al., 2003 [4]. This may necessitate multiple insertions at the same biopsy site to successfully sample the target. Second, current state-of-the-art US guided biopsy technique is highly dependent on the skill of the surgeon. The surgeon performs this procedure by holding the US probe with two or three fingers of one hand while using the other two or three fingers to stabilize the breast, and inserts the needle with the other hand. Since 2D sonography only provides image of a planar cross-section, if the target moves out of plane of the US probe, the surgeon has to continuously reorient the US probe to keep the needle and the target in the imaging plane while inserting the needle. It is critical to orient the imaging plane parallel to the needle, otherwise a false impression of the needle tip causes sampling errors. Since stabilization of the breast is problematic and steering of the needle inside the breast is extremely difficult, many insertion attempts may be required to successfully sample the target. This may cause architectural damage to the tissue, excessive bleeding obscuring the guiding images, surgeons' fatigue and patient discomfort.
Currently available commercial biopsy instruments (Mammotome®, Vacora® etc.) do not compensate for target movement during needle insertion. Robotic systems to improve the accuracy of needle insertions (see: Stoianovici et al. 1998 [5] and Cleary et al., 2001 [6]) do not provide real-time trajectory correction to overcome error due to target movement. In Okazawa et al., 2005 [7], DiMaio et al., [8] and Glozman et al., 2007 [9], steerable needle techniques are presented that allow steering the tip of the needle towards the target during insertion. Steerable devices can only be used with small caliber needles and hence are unsuitable for core needle biopsies. A visually controlled needle-guiding system is developed in Loser et al., 2000 [10], for automatic or remote controlled percutaneous interventions. Though this system potentially reduces the number of insertions required to sample the target, maneuvering a needle inside the breast causes tissue damage. In Azar et al, 2002 [11] and Alterovitz et al., 2003 [12], a finite element model of the breast is used to predict the movement of the target. The needle path is planned based on this prediction to accurately sample the target. To get an accurate prediction of the movement of the target, finite element analysis requires the geometric model and mechanical properties of the breast. In [11], the average time for computation is 29 minutes.
Researchers have developed robotic systems to alleviate the difficulty associated with acquiring US images during medical procedures. A force controlled robotic manipulator for performing cardiovascular 3D US image acquisition has been presented in Pierrot et al, 1999 [14]. Teleoperated master/slave robotic systems have been developed that enable remote acquisition of US images. See: Masuda et al., 2001 [15] and Vischis et al., 2003 [16]. A needle driver robot is presented in Hong et al., 2004 [17] where two degrees of freedom (DOF) in the US image plane are controlled through visual servoing. In this approach the needle is constrained to lie in the US image plane for visual feedback. This idea is extended in Vitrani et al., 2005 [18], where the controlled instrument is not constrained to lie in a plane but has to intersect with the US image plane. An image guided robot for positioning the US probe and tracking a target in real-time has been developed for diagnostic US Abolmaesumi et al., 2002 [19]. The robot controller, US image processor and the operator have shared control over the robot for guiding the US probe.
Even though these systems greatly reduce the difficulty of acquiring US images, the target cannot be tracked in real-time if it moves out of the imaging plane of the probe. In Krupa et al., 2007 [20], a speckle decorrelation technique is presented for estimating out-of-plane motion of a target. Simulation results presented assume rigid motion of internal tissue to preserve correlation between successive image planes. Due to needle insertion and target manipulation, large tissue deformation occurs inside the breast which prohibits application of this technique.
Force sensors are typically used to ensure contact between the surface and the US probe [14][16][19].
A hybrid controller is needed for coordinating multiple systems for robotic biopsy is needed. There has been some work on developing such hybrid controllers in other non-analogous fields, such as industrial robotics, medicine and manufacturing (see: Antsaklis, 2000 [23]), however no work has been done with respect to such a system for biopsy purposes.